Application of the surface response methodology (RSM) to optimise alkaline leaching of vanadium and molybdenum from man-made raw materials

Abstract

The growing demand for strategically important metals, coupled with the depletion of high-quality ores, has highlighted the potential of man-made waste as a secondary source of vanadium and molybdenum. This study investigates the alkaline leaching of technogenic vanadium-containing waste (filter cake) using sodium hydroxide (NaOH) and sodium hypochlorite (NaOCl) as an oxidiser. Chemical and X-ray fluorescence analyses confirmed significant contents of vanadium (3.44%), molybdenum (0.75%), and other valuable metals, indicating the feasibility of complex metal recovery. An experimental design based on the response surface methodology (RSM) and a central composite plan was employed to evaluate the effects of leaching time, reagent concentration, pH, and temperature on metal extraction. Quadratic regression models were constructed and validated using analysis of variance (ANOVA), demonstrating high adequacy (vanadium: F = 9.55, p < 0.001; molybdenum: F = 9.84, p < 0.01). Under optimal conditions, extraction efficiencies were 88–89% for vanadium and 80–82% for molybdenum, increasing to 89–93% and 82–83%, respectively, with the addition of NaOCl. X-ray phase analysis revealed the formation of stable aluminium and nickel oxide phases, which partially limited extraction and explained deviations from predicted values. The results demonstrate that combining alkaline leaching with an oxidiser and statistical modelling enables effective optimisation of multicomponent waste processing, enhancing metal recovery and reducing environmental impacts, thereby providing a basis for resource-efficient, environmentally friendly metallurgical technologies in Kazakhstan.